The present invention relates to an axle assembly for use on trailers, automobiles and other vehicles. More particularly, the present invention relates to an axle assembly which includes a pair of one piece trailing arms each having a plurality of elastomeric bushings thereon. This assembly is inserted into a housing which is then connected to the vehicle""s frame.
Trailers are designed to be attached to a conventional automobile or light truck through the use of a trailer hitch. These trailers are designed to haul some type of cargo and generally they have single or multiple axle units to support their weight and the weight of their cargo. Most trailers are rated up to about a 7000 pound capacity and this capacity can increase with the use of additional axles.
Prior art trailers have been built with steel leaf springs as a part of the axle assembly for the purpose of absorbing shock. These leaf springs are fixed to the trailer frame with the trailer""s axle being positioned below the spring. This method of supporting the load and absorbing the shock is both functional and relatively inexpensive. One of the problems associated with this method of supporting the load is that a single axle will transmit shock between the two wheels. This transmission of shock increases sway, affects trailer tracking and promotes instability. In addition, if the leaf springs are not sufficiently damped, it is possible for the trailer to reach a point of resonance. This resonance could cause an uncomfortable ride, result in a loss of control of the vehicle and/or cause serious damage to the vehicle.
Because of the problems noted above and others, the trailer industry has converted over to using rubber torsional springs in the axle assemblies as a substitute for leaf springs. The rubber torsional springs are part of an axle assembly that includes an outer housing which is typically secured to the frame of a trailer, an inner member disposed within the outer housing, a plurality of bushings disposed between the inner member and the outer housing, a separate linkage or activating arm attached to the inner member and a separate spindle attached to the linkage or activating arm. The spindle has a hub attached to it which supports a wheel assembly. Rubber torsional spring axle assemblies are particularly advantageous for users of trailers that have more delicate items such as boats, horses, snowmobiles, etc. When using rubber torsional bushings, trailers generally pull better, they are not subject to resonant vibration and they provide a better overall ride.
When designing the axle assembly using rubber torsional springs, it is preferable to have the rubber work in compression rather than shear since rubber is stronger in compression and weaker in shear. Also, it is preferable to have the axle assembly permanently sealed and it is preferable to limit the number of individual components needed to assemble the axle assembly to help reduce the overall costs and complexities of the axle assembly.
The present invention provides the art with a trailer axle assembly which includes an outer housing, an inner member and a plurality of bushings disposed between the inner member and the outer member. The inner member includes a unitary longitudinal shaft, activating arm and spindle. The unitary design for the inner member reduces the number of pieces needed for the inner member along with the costs associated with machining the various individual pieces of the prior art systems.
In one embodiment of the present invention, the spindle is a separate component which is then welded to the unitary longitudinal shaft and activating arm.